Extraction of beryllium from ores

ABSTRACT

THE EXTRACTION AND THE RECOVERY OF BERYLIUM SUBSTANTIALLY DEVOID OF ZINC AND OTHER IMPURITES FROM LOW AND MEDIUM GRADE ACID-LEACHABLE BERYLLIUM BEARING ORES IS ACCOMPLISHED BY ACID-LEACHING AT A PH IN THE RANGE FROM ABOUT 1.2 TO ABOUT 2, PREFERABLY BETWEEN 1.3 AND 1.5, AND ADVANTAGEOUSLY WITH THE AID OF A SOLUBLE FLUORIDE ADDITIVE FOLLOWED BY RAISING THE PH OF THE LEACH LIQUOR INITIALLY TO ABOVE 3.0 BUT BELOW ABOUT 4.5 AND FINALLY TO ABOVE 7.5 BUT BELOW 9.0 TO PRECIPITATE BERYLLIUM HYDROXIDE THEREFROM. IN THE INITIAL PH RAISING STEP, ALUMINUM IS PRECIPITATED FROM THE LEACH SOLUTION. AFTER FILTRATION TO REMOVE THE PRECIPITATE, A CHELATING AGENT SUCH AS EDTA MAY BE ADDED TO THE FILTRATE PRIOR TO THE SECOND PH RAISING STEP FOR THE PRECIPITATION OF BERYLLIUM VALUES THEREFROM. THE PRECIPITATED BERYLLIUM HYDROXIDE IS FURTHER PURIFIED BY REDISSOLUTION HYDROLYSIS IN SODIUM HYDROXIDE SOLUTION. ALTERNATIVELY, IT MAY BE TREATED WITH STRONG AND HOT CONCENTRATED SULFURIC ACID PRIOR TO THE PRECIPITATION OF BERYLLIUM VALUES AS A HYDROXIDE. THE ZINC IS REMOVED FROM THE FINAL BERYLLIUM PRODUCT BY TREATING THE LEACH LIQUOR WITH A SOLUBLE SULFIDE AFTER THE INITIAL PH RAISING STEP OR BEFORE THE HYDROLYSIS OF THE REDISSOLVED BERYLLIUM HYDROXIDE.

No v I8 1972 J. K. GRUNIG Filed Dec. 21, 1970 CRUSHED BeO ORE 2 Sheets-Sheet 1 PREGNANT SOLUTION CRUDE HYDROXIDE HYDROLYSIS NH3 ROD MILL SOLUBLE 93% i I I FLUORIDE I I I p H 1.4 BATCH ACID LEACH BATCH PRECIPITATION FILTRATE FILTER LOAD TANK I SULFIDE PRECIPITATION I EDTA 'REG ENERATION CAKE 50% N0 OH I P 1 CAUSTIC 0 I6 ESTION FILTER SOLID RESIDUE I J To TAILINGS FILTEI'? I- I I 5 E J I FILTRATE CAKE 50% NoOH REPULPER I It FILTER CAKE Fl TRATE DEIONIZED WATER I I FLAKE NuOH REPULPER L FILTER CAKE FILTRATE WASTE INVENTORS JAMES K. GRUNIG WILLIAM B. DAVIS FIG. :I WILLIAM C.AITKENHEAD E'Y W 5mm "y 'p ATTORNEYS NOV 28, 1972 R ETAL 3,704,091

EXTRACTION OF BERYLLIUM FROM ORES Filed Dec. 21, 1970 I 2 Sheets-Sheet 2 ROCEDURE s) EXCESS H2'S04' r '1 I I i I S'UJFATE DEIONIZED H2O I I CONVERSION I DILUTION] "159 995 A) 10% 2 Fl Em I -9870 H2504 I I I SULFATE SULFIDIZATIONI I t I CONVERSION I I I a TER FILTRATE QA Q I l HYDROXIDEV v I PRECIPITATION I I H2304 I s. and F REMovAL P- --EDTA I CONC.SULFURIC CAKE FILTRATE I ACID TREATMENT NH CHELATION I EMA-" y DISCARD 1 3 HOLDING TANK(BOIL) NH CHELATION I l "'T L I I L J I DEBERYLLIZATION uPRocEouRE c) CONC.SULFURIC I ACID TREATMENT I DECANTATION TANK L f DEIONIZED H2O WASHER SETTLINGS DECANTATE DECANTATE SETTLINGS FILTER DEIONIZED M o-I FILTER (15g FILTRATE To DISCARD FILTRATE CAKE To DISCARD Be(OH)2 T DRYER DRlED Be(0H)2 BeIOHIZ PRODUCT CALCINATION BeO PRODUCT INVENTORS JAMES K. GRUNIG WILLIAM B. DAVIS United States Patent 3,704,091 EXTRACTION OF BERYLLIUM FROM ORES James K. Grunig and William B. Davis, Tucson, Ariz.,

and William C. Aitkenhead, Belize, British Honduras,

assignors to The Anaconda Company, New York, N.Y. Continuation-impart of application Ser. No. 710,984, Mar.

6, 1968, which is a continuation-in-part of application Ser. No. 316,474, Oct. 15, 1963. This application Dec.

21, 1970, Ser. No. 99,852

Int. Cl. C221) 59/00 U.S. Cl. 423128 11 Claims ABSTRACT OF THE DISCLOSURE The extraction and the recovery of beryllium substantially devoid of zinc and other impurities from low and medium grade acid-leachable beryllium bearing ores is accomplished by acid-leaching at a pH in the range from about 1.2 to about 2, preferably between 1.3 and 1.5, and advantageously with the aid of a soluble fluoride additive, followed by raising the pH of the leach liquor initially to above 3.0 but below about 4.5 and finally to above 7.5 but below 9.0 to precipitate beryllium hydroxide therefrom. In the initial pH raising step, aluminum is precipitated from the leach solution. After filtration to remove the precipitate, a chelating agent such as EDTA may be added to the filtrate prior to the second pH raising step for the precipitation of beryllium values therefrom. The precipitated beryllium hydroxide is further purified by redissolution and hydrolysis in sodium hydroxide solution. Alternatively, it may be treated with strong and hot concentrated sulfuric acid prior to the precipitation of beryllium values as a hydroxide. The zinc is removed from the final beryllium product by treating the leach liquor with a soluble sulfide after the initial pH raising step or before the hydrolysis of the redissolved beryllium hydroxide.

CROSS-REFERENCE TO A RELATED APPLICATIONS This is a continuation-in-part application of our application Ser. No. 710,984, filed Mar. 6, 1968 and now abandoned, which in turn is a continuation-iu-part of our application Ser. No. 316,474, filed Oct. 15, 1963, entitled, Precipitation of Beryllium From Ore, now Pat. No. 3,395,975.

BACKGROUND OF THE INVENTION (I) Field of the invention This invention relates to a process for the extraction and recovery of beryllium in the form of substantially pure beryllium compounds from beryllium bearing ores. More particularly, this invention relates to a process for the extraction of acid-leachable beryllium values from ores in a manner permitting easy separation of those values from other mineral components in the ores. The process of this invention is particularly suitable for recovering beryllium values from low and intermediate grade ores.

(II) Description of the prior art Several processes for the extraction of beryllium values from ores have been developed, some of which are'only 3,704,091 Patented Nov. 28, 1972 "ice suitable for acid-leachable beryllium values. In these prior art processes, it has been diflicult to separate com-- pounds of aluminum, iron, magnesium, and calcium from the beryllium compound component. Hence, the final beryllium product is rather impure. It has, heretofore, been proposed to extract beryllium compounds from beryllium bearing ores by leaching with acid, and-then causti BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1 and 2, taken together, are a flow sheet of the process in accordance with the present invention and its alternatives for producing substantially pure Be(OH) SUMMARY OF THE INVENTION We have found that the autoclave can be eliminated and that the recovery of substantially pure beryllium compounds can be achieved by other means. The process of the present invention comprises treating a beryllium bearing material containing aluminum, iron, fluorine, and other impurities with a mineral acid at a pH below 2.0, not below 1.2, to extract the beryllium and a minimum of impurities from the material. The acid slurry then is heated and its pH carefully raised to above 3.0 but below about 4.5, and preferably below 4.0, to cause the precipitation of fiuoro-compounds of aluminum and compounds of iron. The precipitates are separated from the leach liquor by filtration and the pH of the filtrate is then further raised to above 7.5 butbelow 9.0 causing the precipitation of beryllium from the solution. A minor amount of impurities are also concurrently precipitated. The beryllium precipitate is recovered and digested in a sodium hydroxide solution. The beryllium in the sodium hydroxide solution is then hydrolyzed and reprecipitated as beryllium hydroxide thus precipitating values rich in beryllium. Alternatively, the beryllium precipitate is treated with a strong sulfuric acid and the beryllium values are subsequently recovered as a hydroxide precipitate.

The zinc impurities, preferably, are removed by treating the leach liquor with a soluble sulfide after the initial pI-I-raising step or before the hydrolysis of the digested beryllium hydroxide.

DESCRIPTION OF THE PREFERRED EMBODIMENT The success of the process of this invention is based on the discovery that by carefully controlling and raising the pH of the hot leach liquor in two successive steps, the major portion of troublesome aluminum, iron and fluorine impurities can be eliminated. The successive pH- raising steps coupled with the subsequent'beryllium'hydroxide redissolution and hydrolysis steps produce a substantially pure beryllium compound devoid of undesirable contamination.

' A number of beryllium ores are suitable for treatment by the method of the present invention, such as Spor Mountain and Topaz Mountain ores. The beryllium in Spor-Topaz ores is thought to be contained in the mineral bertrandite, Be Si O-,(OH), and in beryliferous saponite, a clay-like mineral, both of which are soluble in moderate concentrations of mineral acid. In contrast to bertrandite, beryl (3BeO-Al O -6SiO and phenacite (Be SiO other forms of naturally occurring beryllium, are not readily soluble in moderate acid concentrations, but may be rendered acid soluble by prior art processes including fluoride sintering or alkali fusion. Spor-Topaz ores are thus susceptible to leaching directly by mineral acid and may therefore be advantageously used in the process of this invention. Other ores containing beryllium values, when rendered acid-soluble by prior art methods, may also be used in the process herein.

Following is a detailed description of a beryllium recovery operation embodying the invention, presented with reference to the accompanying two sheets of drawings which together show a single flowsheet of a specific procedure and its alternatives for producing substantially pure Be(OH) The dotted line shows the alternative procedures.

Referring to the drawing, the beryllium ore (after it is ground to the desired size) is acid-leached with sulfuric acid. Instead of sulfuric acid, hydrochloric acid may be used although sulfuric acid is preferable because of lower costs. Spor-Topaz ores may be leached with conventional acid leach liquids having a pH substantially below 1.0, but in accordance with the invention, the ore is leached preferably with H 80 the pH of the leach solution being maintained above about 1.2 and below about 2.0 throughout the duration of the leaching operation. The temperature of the leach solution is in the range from about 160 F. to just below the boiling point of the leach liquor, and the leaching operation proceeds for a period sufficient to dissolve substantially all the beryllium values in the material. Leaching may be at a temperature higher than boiling, in which case pressurized equipment is used. In the process the pH of the acid solution is maintained above about 1.3 during one or more major portions of the leaching period, e.g., for periods of two to three hours at a time, so that the amount of impurities which leach from the ore and enter the leach solution, such as aluminum, iron and fluorine, are kept at a desirably low and controlled level. The pregnant acid solution then may be recovered for further treatment to extract high purity beryllium therefrom.

Preferably, the leaching operation is carried out in a controlled manner so that the pH values are maintained throughout its duration in the range from about 1.3 to about 1.5. When the leaching is conducted at a pH of about 1.4, it requires, typically, using about 450 pounds of H 50 per ton of ore. This amount of acid-leach solution used should be suflicient to result in a slurry containing from about 25% to about 33% of solids.

' The time required to leach the ores may vary within a Wide range depending on leaching conditions which include the pH, the leaching temperature, and the solids concentration. We have found that the amount of available fluoride in the leach solution has a direct bearing on the rate of leaching. Leaching Spor-Topaz ores using an acid-leaching solution at the preferred pH of about 1.4 and at a temperature in the range between 160 F. and 200 F., and with a slurry containing about 25% solids by weight, a period of about 20 hours is normally required for the leaching operation. This period, however, can be drastically reduced if the available fluoride content in the leach solution is raised by the addition of a soluble fluoride. By providing as little as 0.3 g./l. of excess fluoride in the liquor, the leaching time may be reduced to about 6 hours.

The exact reason for the dramatic improvement in the leaching time is not yet certain. It may be due to the fact that, in leaching, beryllium goes into the solution as a fluoro-complex, and, therefore, the rate of leaching is dependent on the fluoride ion activity. If a fluoride is made available only through the following reaction:

then the diflusion rate of H and HF through the CaSO, layer on the fluoride is an inherent limitation of the leach rate. The addition of a soluble fluoride, such as NaF, releases hydrogen fluoride which in combination with sulfuric acid allows the beryllium dissolution to take place at a faster rate.

Any .soluble fluoride which can be readily dissolved in the acid leach solution and which does not materially con tribute to the impurities in the final BeO product may be used. Among them, NaF, NH F, NaI-IF NHJ-IF HF and AlF are eminently suitable. The amount of soluble fluoride that can be added to the solution is not especially critical and depends to a large extent on the amount of available fluoride in the leach liquor. In general, even a trace amount provides beneficial results. Usually an addition above 3 g./l., preferably in the range of 3 to 5 g./l., of the leach liquor based on the Weight of the fluorine seems to be effective for reducing the leaching time to the suitable short duration.

The upper limit as to the amount of fluoride that can be added is not critical. An amount far above that required for the combination with the beryllium values usually is not required. Spor-Topaz ores, the fluoride addition required to combine with the beryllium values therein seldom exceed 10 g./l. of the leach liquor based on the weight of the fluorine.

The fluoride may be added directly into the ore prior to the addition thereto of the acid leach solution, or it may be added directly to the leach solution. Preferably, the fluoride addition is made soon after the major acid addition to form the resultant slurry. The time at which the fluoride may be added to the leach liquor, however, is not very critical as long as its addition provides free fluoride ions for the formation of beryllium fluoro-co'rnplexes.

In addition to the aforesaid soluble alkali fluorides, certain soluble aluminum salts, particularly AlF may be used as additives to facilitate the leaching operation. AlF when added into the acid leach liquor forms AlF++ and AlF ions, the presence of which decrease the solubility of aluminum and have the added benefit of supplying the fluoride ions required for the leaching. The lowering of the aluminum solubility is due to the oifset of the equilibrium conditions within the leach liquor wherein both the beryllium and the aluminum compete for the fluoride ions to form the soluble fluoro-complexes.

The preferred leaching method of this invention as described is superior to the conventional leaching methods which use more strongly acid leach solutions having pHs substantially below 1.2 (typically about 1000 pounds of acid per ton of ore). The lower concentration of acid in the leach solution also provides savings of alkali required in the subsequent pH raising step of the process and has the additional advantage of maximizing the extraction of beryllium values While minimizing the solubilization of other mineral impurities which would otherwise be soluble in a more concentrated acidic solution.

The slurry at this point can be filtered or it may be further processed without filtering. -(T he filtering step is not shown in the accompanying flowsheet.) Filtering and washing at this stage are generally more rapid and have the advantage of requiring less alkali in a subsequent partial neutralization step. If filtration is used, the residue is treated with a series of displacement and repulp washes using hot leaching solution. The residue washings are used advantageously as make-up solutions for the subsequent leaching operation. With or without filtering, the leach solution recovered from the ore contains in solu- BeO 2.3 A1 6.5

MgO 7.2 Mn .02 Zn .16 F 6.4

The impurities in the leach liquor are sufliciently low for it to be suitable for further treatment using the two successive pH raising operations to recover substantially pure beryllium therefrom. This part of the process comprises raising the pH of a leach solution containing beryllium together with aluminum, iron, fluorine, and other impurities to above 3.0 but below about 4.5, add preferably above 3.8 and below 4.2, to cause the precipitation of fluoro-compounds of aluminum and compounds of iron. The precipitates are separated from the leach liquor by filtration and the pH of the filtrate is then further raised to above 7.5 but below 9.0 causing the precipitation of beryllium hydroxide from the solution.

For the initial pH raising operation, a base chosen from NH NH OH, NaOH, KOH, milk of lime or equivalent carbonates or oxides, and organic bases such as urea, is introduced gradually into the heated acid leach solution until its pH has been uniformly raised to a value below about 4.5 but above 3.0, preferably in the range from about 3.8 to about 4.2. (The pH used here is inversely temperature dependent.) At this pH, almost all the iron is precipitated as a basic ferric salt and a substantial portion of the aluminum is precipitated as a l1ydroxyfluoride.

The stability of aluminum hydroxyfluoride is dependent on the temperature and the pH of the leach solution. Ap parently, the higher the temperature, the more stable is the aluminum hydroxyfluoride over a wider pH range. Thus, in our prior process, the removal of the aluminum and fluoride impurities in the leach solution required autoclaving the leach solution at a temperature in the range between 300 and 600 F. At lower temperatures, e.g., below 212 F., as now contemplated, the precipitation of the aluminum hydroxyfluoride, unless carefully controlled in accordance with the invention, tends to be incomplete and takes longer. We found that a higher pH is required if a suflicient amount of aluminum is to be recovered, in other words, to be removed from the leach solution. However, the pH of the solution should not be so high as to cause undesirable co-precipitation of beryllium.

Using lower temperatures, the precipitation of aluminum hydroxyfluoride is further complicated by the competing activities of fluoride and hydrogen ions. It has been found that higher fluoride activity tends to promote precipitation. In leach solutions with a pH in the range of 1.0 to 4.5, the fluoride activity is inversely proportional to the activity of the hydrogen ions. Increasing the activity of the fluoride ions accompanies an increase in pH and in the activity of hydroxy ion which tends to promote precipitation of beryllium. We found that below this pH range, the amount of aluminum hydroxyfluoride precipitation is very small unless the temperature of the solution is greatly increased as to require autoclaving, and above this range undesirable co-precipitation of beryllium is observed.

It is important to note that precipitation according to the present invention is not to be confused with the prior art fractional hydrolysis for the removal of aluminum in acid leach solution which will not work in the present case because of the presence of fluoride ions in the leach solution.

The leach solution, after 4 or 5 hours of hot F. or greater) precipitation at a pH of about 4, is filtered clear to eliminate all residual and precipitated impurities. A typical clear leach solution contains substantiallythe following (in g./l.):

BeO

The filter cake is washed and then discarded. It has been found that if the ore residue is not filtered from the leach solution prior to adjusting the pH to near 4, more of the dissolved beryllium appears to be absorbed by the clayey material in the filter cake than if the filtration were made. In such instances, complete washing is diflicult. By cationic displacement using such chemicals as sulfuric acid and/or ammonium sulfate in the wash water, the absorbed beryllium can be more easily washed from the clay. A considerable amount of wash water may be employed since the washing can be used in making up the next batch of acid leach solution.

If milk of lime (Ca(OH) is used to raise the pH initially to above 3.0 but below 4.5 and in the presence of Na+, aluminum will precipitate not only as hydroxyfluoride of the formula:

but also coprecipitate with sodium, magnesium and fluorine in the form of the mineral ralstonite of the following formula wherein x=Al=1.6 and y=0.1.

The optimal conditions for precipitation with milk of lime in the presence of Na+ vary with the process variables. We found precipitation of impurities at a pH of about 4.0 and at a temperature about 200 F. to be eminently suitable. The retention time at this temperature is about 6 hours. The retention can be reduced at a Using milk of lime for the pH raising together with Na it is possible to obtain BeO/Al O ratio in the range between 5 to 10 as compared to the ratio of 1 to 3 for the pH raising operation wherein aluminum is precipitated only as hydroxy-fluoride.

The sodium in the leach solution required for the ralstonite precipitation may be provided by the soluble sodium fluoride used for facilitating the leaching operation. It may also be provided by adding to the filtered leach solution a sodium salt Which'will not interfere with the formation of the ralstonite or with the subsequent recovery of beryllium values. Sodium sulfate or sodium fluoride (the latter may be used for the-leaching) are found to be eminently suitable.

After the precipitation, the leach solution is filtered and the filter cake may be treated-in the same manner as described for the hydroxyfluon'de precipitation.

Subsequent to the removal of the ore residue, ammonia or another suitable base is again used to raise the pH of the clarified filtrate to a higher pH between 7.5 and 9.0 and preferably in the range of 8.0 to 8.5. At this pH range, beryllium in the form of beryllium hydroxide is Percent BeO 22.0 A1 5.60 Fe 0.06 MgO 17.16 Mn 0.08 Zn 0.06

-In the second pH raising step, a number of alkalies (e.g., sodium or potassium hydroxide, or even lime or calcium carbonate) may be used, of which ammonia, however, is preferred because of its low cost and its ability to complex with a number of metal ions, particularly zinc, to form soluble complexes. The beryllium precipitation may be carried out at a temperature above about 160 F. but preferably below the boiling point of the solution.

Heavy metal ions particularly Zn++ remaining in the leach solution after the initial pH raising step and subsequent filtration may be removed prior to the second pH raising step using soluble sulfide to precipitate the heavy metal ions as sulfides as shown by the dotted line in the accompanying flow sheet. The sulfide precipitation step removes substantially all zinc ions in the solution (solutions containing 50 parts per million zinc before treatment with a soluble sulfide treatment typically containing less than 1 part per million afterwards) as well as other heavy metal ions such as copper, cadmium, and lead.

For many applications, the zinc level of BeO is preferably less than 1000 ppm. which corresponds to a zinc concentration less than 0.001 gm./liter in the pregnant solution after initial precipitation at a pH of about 4.0. At this low level of zinc concentration, and at the pH range between 3.5 to 4.0, the removal of the zinc ion by the addition of the sulfide ion (desirably but not exclusively H 8) is readily controlled by measuring the electromotive force (EMF) of the solution. For example, We found a gold electrode with a silver-silver chloride reference can be used to monitor the change in EMF. When the gold electrode and its reference are tested in a ferrocyanide-ferriccyanide standard solution, an EMF of 172 millivolts is obtained, and using a platinum electrode and a hydrogen reference, the EMF is 428 millivolts. We found that the zinc precipitation is substantially completed when the EMF between the gold electrode and the silver-silver chloride reference electrode is 250 millivolts. Of course, it is understood that the EMF would be different if a different pair of electrodes were used. In such cases, the difference between the new EMF and 250 millivolts would equal the difi'erence between the reading of the new electrode pair in the standard solution and 172 millivolts.

A preferred procedure for zinc and other heavy metals removal from the pregnant pH 4.0 solution is to heat the sol ution in the sulfidization tank to about 140 F. and thereafter to introduce the gaseous H S into the solution until the EMF of the gold and silver-silver chloride electrodes reaches 250 millivolts and is maintained at that level for one-half hour. The level of zinc in the solution can be checked in a conventional manner such as with dithizone. When the zinc level is Within the requirement (below 0.001 grarn/ liter), the solution is filtered and thereafter the filtrate is tested again with dithizone to assure the zinc level therein is less than 0.001 gm./

liter. If the zinc level is above the required level, additional sulfide is used to bring the level down to requirement. Additional filtering is used to remove the precipitates therein.

After the removal of the heavy metal ions and prior to the second pH raising step, a chelating agent, preferably ethylene diamine tetraacetic acid ('EDTA), may be used to complex with the filtrate (pregnant solution) from the sulfide precipitation tank as shown by the dotted line in the accompanying flow sheet. It is important that the chelating agent is added after the sulfide precipitation since most of the heavy metal ions removed in the earlier treatment chelates with EDTA to form stable soluble chelates which cannot be readily broken up in the subsequent regeneration step for the recovery of EDTA. The sulfide precipitation reduces the concentration of cations which chelate with EDTA to form stable complexes. Normally, after sulfide treatment, the pregnant solution contains only a low concentration of Mn+++ and Fe+++ cations whose chelates cannot be broken up. We have found that of the impurities present only fluorine, sodium, and silica do not chelate with EDTA. Advantageously, EDTA is first dissolved in a pH 5.5 solution prior to its addition to the pH 4.0 pregnant solution. An excess amount of EDTA is used to insure complete complexing of all chelatable cations therein to for mthe soluble complexes. A retention time of several hours (2 to 10 hours) at the temperature range of to F. is preferably used to allow the slow chelating cations such as Al and Fe+++ to form the complexes.

Following chelation, the pH of the solution is raised to the desired pH range above 7.5 but below about 9.0 in the manner described. It is noted that the presence of the fluorine ions has retained the beryllium values in the solution until the higher pH values are reached at which time the beryllium is precipitated as hydroxide.

After the beryllium hydroxide precipitate is recovered by filtration, the filtrate containing the EDTA complexes is treated to regenerate EDTA for recycling. The filtrate generally contains the EDTA complexes of Ca, Mg, Al, Mn, and Fe and some free EDTA. The alkaline earth and alkali metal complexes are regenerated easily by acidifying the filtrate to a pH of about 1.8. The aluminum chelate can be regenerated by lowering the pH to about 1.4. The complexes of Mn+++ and Fe+++ which cannot be regenerated are not recovered, the amount of which, however, is small compared to the total amount of EDTA recovered. The regenerated as well as the excess EDTA is precipitated from the acidified solution and is recovered by filtration.

The successive pH raising steps remove a major amount of impurities from the original leach solution. The beryllium filter cake may be further treated by conventional methods for removing the impurities. Further purification treatment, however, should be selected according to the impurities in the beryllium filter cake.

One of the treatments, which is particularly suitable for use in combination with the double pH raising steps without the chelating treatment, comprises the steps of digesting the impure hydroxide in a strong alkali solution for a period suflicient to dissolve substantially all the beryllium values in the solution. After the insolubles are separated from the digesting solution, the beryllium solution is hydrolyzed to cause the precipitation of beryllium hydroxide. The precipitated beryllium hydroxide is then recovered from the solution.

Advantageously, the filter cake containing beryllium recovered from the double pH raising steps is digested in a 50% solution of sodium hydroxide. The temperature of the slurry, which tends to increase during digestion, advantageously is controlled by external cooling. The slurry is filtered, and the recovered filter cake is further treated with more 50% sodium hydroxide solution and refiltered. This second filtrate, after addition of solid sodium hydroxide to bring the concentration to 50%, is recycled and is used to make up part of the solution for digestion of the BeO 0.7 Na 35 F 25 MgO 7 A1 5 CaO 2 Water of hydration The cake is composed chiefly of crystallized NaF and NaF-Na SO and is discarded.

As stated hereinabove, the first strong sodium hydroxide leach filtrate preferably is combined with the water repulp filtrate, and additional deionized water is added to bring the NaOH concentration to about 1.5 N. This diluted sodium hydroxide solution usually contains 4 to '5 g./l. BeO together with some aluminum and a very small amount of zinc (if the prior sulfide precipitation is not used or the step has not completely eliminated it). Because zinc and beryllium have a tendency to coprecipitate, the small amount of zinc must be eliminated before the final hydrolysis step if low zinc content in the final beryllium produce is to be achieved. The zinc elimination step may be carried out by adding a solution of a sulfide such as sodium sulfide solution to the diluted NaOH solution to cause the precipitation of ZnS. The zinc precipitate is filtered or otherwise separated by conventional methods and is discarded.

Subsequent to dilution and zinc removal, the solution in a suitable holding tank is brought to boiling by external heating for a period of time sufiicientfor all Na BeO to hydrolyze to Be(OH) which precipitates out of the solution while the aluminum remains therein. In the beryllium precipitation (deberyllization) step, boiling for two hours is generally adequate. The precipitate, which is readilyfiltered because it is granular in character, is subjected to a series of decantings, washings, and filterings as shown in the accompanying flow sheet to remove traces of impurities. Deionized water preferably is used to wash the settlings from the decantation tank after deberyllization as well as from the washer. The cake recovered may be dried to Be(OI-I) The final product meets the fololwing specification:

The Be(OH) recovered may be fired at about 1600 F., or higher, to produce BeO. The overall recovery by this process is, in a typical pilot plant run on ore containing 1% BeO, approximately 75% of the assayed BeO in the ore.

The crude beryllium hydroxide recovered as the precipitate from the second pH raising step may be subjected to a number of other alternative treatmentsas shown in the flow sheet to produce the high purities required. Thus,

10 in one preferred procedure identified in the flow sheet as Procedure A, the filter cake containing the impure beryllium hydroxide is added to a concentrated sulfuric acid (98% H 50 or higher) in an amount sufficient or slightly in excess to convert stoichiometrically all the metals to sulfates (sulfate conversion). The conversion step is highly exothermic, and the heat of the reaction will cause continuous fuming at 300 F. to 600 F. until a semi-dry cake is obtained. The hydrogen fluoride as well as S0 generated from the conversion reaction may be recycled to the leaching solution to facilitate the dissolution of the beryllium in the leaching process described hereinabove.

The semi-dry sulfate cake is dissolved in water and the pH of the resultant solution is adjusted to about 7.0 and 8.0 by the addition of caustic therein. The pH raising step causes the precipitation of the hydroxide which is recovered by filtration. Optionally, the cake may be washed with water. After washing, the hydroxide cake is reslurried in a sufiicient amount of water to prepare a relatively thin slurry (10% by weight of solids). The slurry of hydroxide is then added rapidly to concentrated sulfuric acid to produce boiling aggregates containing beryllium sulfate. Additional boiling for 30 minutes to an hour or even more may be used to insure the complete conversion of the hydroxide to the soluble sulfate. The fluorine in the slurry is volatilized to some extent, and silicon is mostly dehydrated. The impurities remaining in the form of insolubles are removed by filtration. The filter cake may be washed once or more to recover the soluble beryllium. After washing, the filter cake may be discarded. In these successive sulfuric acid treatments, the initial H fuming step and the sulfuric acid boiling operation may be interchanged. When the fuming step is used in the second stage of the process, the semi-dry sulfate cake obtained is redissolved in water before it is subjected to further purification treatment.

In the next purification step, if chelating agent such as EDTA'has not been used in an earlier process step, it is preferably added at this time to form soluble complexes with other impurities before the sulfate solution is subjected to a pH raising operation with a caustic to precipitate beryllium as a hydroxide. As described, EDTA may be recovered by acidifying the neutral or slightly alkaline solution to a pH of about 1.0 to 2.0 and followed by filtration to remove the precipitated EDTA which may be redissolved in an alkaline solution for subsequent use.

Alternatively, the dried or moistened beryllium hydroxide recovered from the double pH raising process is treated with a large excess amount of H 80 (preferably 98% or higher) to produce a slurry of insoluble sulfates (identified as Procedure B in the flow sheet). To insure complete conversion, the slurry is heated for about one hour or more at about 300 F. to below about 500 F. The substantially anhydrous sulfates thus formed together with dehydrated silica are removed by filtration. The filtrate may be recycled for treating another batch of impure beryllium hydroxide. The anhydrous sulfates are heated to volatilize the silicon and fluorine ias 'SiF and HP. The HF and 80;, may be recovered for use in the leaching operation. Subsequent to the volatilization step, beryllium sulfate is dissolved in water and is precipitated in the form of hydroxide in a manner described hereinabove. EDTA or another chelating agent may also be used for the preparation of an extremely high purity product.

The alternative procedures of high concentration H 80 treatments in combination with the hydroxide precipitation of beryllium, particularly when it is carried out in the presence of a chelating agent, produce a product with an extremely low silica contamination and also meet low impurity requirements for all other contaminants.

For the process in which the initial pH raising step is carried out with milk of lime and in the presence of Na+ and the subsequent pH raising step is conducted after the chelation treatment, the impurities in the resultant filter cake (beryllium hydroxide) may be sufficiently low that a simplified sulfuric acid treatment can be used (Procedure C). In the simplified treatment, the hydroxide cake is initially slurried with water. The slurry of hydroxide is then added rapidly to a concentrated sulfuric acid (98% H 80 or higher). The acid and water used advantageously are maintained in stoichiometric relations with the amount of Be-(OH) in the slurry for conversion of the latter to 36804-417120. The strong sulfate solution is diluted with water to a concentration preferably about 10 g./l. based on the weight of BeO. The diluted solution is then heated to a range of about 150 F. to just below boiling and preferably to about 170 F.

The impurities remaining in the form of insolubles are removed by filtration. The clear filtrate then is subjected to a pH raising operation as described hereinabove to precipitate the beryllium values. Since fluorine has been substantially removed in prior purification steps, the precipitation may be carried out at a lower pH value. We found a pH of about 7.2 to be suitable.

Precipitation of Be(OH) 2 from the sulfate solution with NH results in a certain amount of (NH SO entrainment in the precipitates which preferably is washed out wtih either NHgCl or water. A small amount of sulfate, which may remain in the final product, is removed in the subsequent calcining operation for converting Be(OH) to BeO. The resultant BeO is devoid of sulfate impurity.

Further to illustrate this invention, specific examples are described hereinbelow with further reference to the accompanying flow sheet.

EXAMPLE I This example represents an average pilot plant run involving a 2-ton batch of ore. In this example, four thousand pounds of Spor-Topaz ore assaying 0.67% BeO is ground in a rodrnill to minus 14 mesh. Water (usually wash water from a previous leach residue filtration) is added to the mill to make up a slurry of about 30% solids. The slurry is allowed to run to a steam-jacketed, 1000-gallon, lead-lined tank equipped with an agitator. Sulfuric acid is gradually added to the tank as needed to maintain a pH continually as close as feasible at about 1.4. The charge is heated to about 180-200 F. and is held at this temperature for about 20- hours. About 900 pounds of acid is added.

After leaching is completed, ammonia gas is introduced to the leach solution slowly over a 4-hour period to bring the pH to about 3.8. The slurry is held at about 180 F. or above for a period of 5 hours. The slurry is subsequently filtered on a Moore filter and is washed thoroughly with a 0.1 M solution of ammonium sulfate to which sulfuric acid has been added to bring the pH to about 3.5. The used wash water is saved for slurrying another batch of ore. The filter cake contains 0.10% BeO, a loss of about 14% of the Be in the ore.

The filtrate is placed in a heated tank and brought to an EMF between 100 and 300 millivolts (as measured by a gold and silver-silver chloride electrode) using H 8 gas. An EMF of about 250 millivolts is preferred at a temperature of 140 F. After this EMF and this temperature are attained, the temperature is allowed to drop gradually while the EMF is maintained at the same level. The precipitate thus formed contains substantially all of the zinc in the original filtrate. The precipitate is removed in a plate and frame filter, the filtrate from which contains less than 1 part per million zinc.

The filtrate is ubjected to a second pH raising step wherein ammonia is again gradually introduced into it to bring the pH to about 8.5. During this operation, the temperature is held at 170 F. The slurry from this operation is filtered on a drum filter. The filtrate containing 0.013 gram per liter BeO is discarded resulting in a loss of 0.7% of the Be in the ore.

The hydroxide precipitate containing about 70% water is next mixed with 24 pounds of cold 50% NaOH solution per pound of BeO in the solution in a water-jacketed tank, and its temperature is kept as close as possible to room temperature. After digestion for at least one hour, the slurry is filtered in a plate and frame filter press. The recovered filter cake is repulped with a 'suflicient amount of 50% NaOH solution to make a pumpable slurry and then is refiltered on a drum filter. This filter cake is repulped with deionized water and filtered once more on a drum filter. The cake containing 0.7% BeO is discarded. This represents a loss of 4.3% of the Be in the ore.

To the filtrate, from the repulping with 50% NaOH, solid NaOH is added to bring the NaOH content up to about 50%, and this solution is reserved for use as part of the caustic for digesting the next batch of crude hydroxides.

The first strong caustic filtrate and the water repulp filtrate are combined with a suflicient amount of deionized water to make the specific gravity equivalent to a NaOI-I content of about 1.5 N. After stirring for one-half hour, the solution is filtered in a plate and frame filter press. The cake consisting substantially of CaSO is discarded. The clear filtrate is boiled in a steam-jacketed tank for 2 hours. The precipitate of Be(OH) is allowed to settle. The supernatant solution is decanted ofif, and the precipitate is washed twice with deionized water (filtered on a pan filter and washed once more on the filter). The filtrate and washings containing 0.73 pound of BeO (2.7% of the Be in the ore) are discarded. The cake is dried and packaged. The dried product contains over 99% Be(OH) EXAMPLE II Analysis of ore (500 gms.)

Percent BeO 0.94 1121 0 8.13 i e 1.75 C'aO 7.90 MgO 2.97 SiO 48.20 Mn 0.03 F 4.39

Ammonium hydroxide was then added until a constant pH of 4.3 was attained. This step required 3 hours. The leach was then filtered and the residue washed. The leach solution and the residue after pH adjustment to 4.3 had the following analysis:

Analysis of leach solution (2660 ml.) in g./l.

BeO 1.6 A1 0 0.45 MgO 2.62 Mn 0.16

Zn 0.02 F 1.8

Analysis of residue (485 gms.)

BeO percent 0.08

The process precipitates the hydroxyfiuorides in the leach itself so a separate analysis is impossible. The following is an analysis of this precipitate made from a leach solution which was filtered after the acid leach (pH 1.5). The solution was brought to a constant pH 4.3 with ammonium hydroxide keeping the temperature at 100" C. About 12 gms. of this precipitate is produced in a test like the one under consideration.

13 Analysis BeO 2.15 A1 30.15 Fe 2.61 MgO 4.71 Mn Nil Zn 0.01 F 34.2

Subsequent to the separation of insolubles, the pH of the leach solution was further raised by the addition of ammonium to a final pH of 8.5. The beryllium was precipitated in the form of hydroxide which had the following analysis:

Analysis of the pH 8.5 filtrate (2660 ml.) in g/l.

1. A process for extracting beryllium values from a beryllium bearing material containing aluminum, iron, fluorine, zinc, and other impurities which comprises leaching said material with a mineral acid at a pH between 1.2 and 2.0 and in the presence of a soluble fluoride for a period sufiicient to dissolve a substantial portion of the beryllium values in said material, maintaining the pH of said acid at above about 1.3 during a major portion of said period, thereby controlling the amount of impurities dissolved therein, raising the pH of the leach liquor to a value above 3.0 but below about 4.5 with milk of lime and in the presence of sodium ions to eliminate a major portion of iron and aluminum in said liquor, separating insoluble matter from the solution, adding to the residual solution a soluble sulfide in an amount sufiicient to precipitate at least a major portion of the heavy metal cations, separating the precipitate from the solution and adding thereto a chelating agent in an amount sufiicient to chelate with the chelatable impurities therein, further raising the pH of the residual solution to a value above 7.5 but below 9 to precipitate beryllium hydroxide and a minor portion of impurities from the leach liquor, adding the hydroxide into a concentrated sulfuric acid solution to convert the hydroxide to beryllium sulfate, diluting the sulfate solution and precipitating therefrom the beryllium values as a hydroxide.

2. A process for recovering beryllium values from a leach solution produced by leaching beryllium bearing material at a pH in the range from 1.2 to 2.0 and containing beryllium together with iron, aluminum, fluorine and other impurities, which comprises initially raising the pH of the leach solution carefully to a range between 3.0 and 4.5 to cause the precipitation of fluoro-compounds of aluminum and compounds of iron, separating the precipitate from the leach solution, further raising the pH of the leach solution to a final pH range between 7.5 and 9.0 causing the precipitation of beryllium hydroxide and a minor portion of impurities from the solution, and recovering the precipitated beryllium hydroxide.

3. A process accordingto claim 2 wherein the pH of the solution is raised initially to a value in the range between 3.5 and 3.9.

4. A process according to claim 2 wherein the leach solution impurities include zinc and a soluble sulfide is added to the leach solution to precipitate zinc and other insoluble sulfides therefrom after its pH has been raised initially to above 3.0 but below 4.5, and the resulting impurities are separated from the solution.

5. A process according to claim 4 wherein H 8 is added to the leach solution.

6. A process according to claim 4 wherein an alkali sulfide is added to the leach solution.

7. A process according to claim 2 wherein ammonia is used to raise the pH of the leach liquor.

8. A process according to claim 2 wherein insolubles are separated from the leach solution prior to raising its pH to between 3.5 and 4.0.

9. A process for extracting beryllium values from a beryllium bearing material containing aluminum, iron, fluorine, zinc and other impurities which comprises leaching said material with a mineral acid at a pH between 1.2 and 2. 0 and in the presence of a soluble fluoride for a period sufiicient to dissolve a substantial portion of the beryllium values in said material, maintaining the pH of said acid above about 1.3 during a major portion of said period thereby controlling the amount of impurities dissolved therein, raising the pH of the leach liquor to a value above 3.0 but below about 4.5 to eliminate a major portion of iron and aluminum in said liquor, separating insoluble matters from the solution, adding to the residual solution a soluble sulfide in an amount sufiicient to precipitate at least a major portion of the heavy metal cations, separating the precipitate from the solution, further raising the pH of the residual solution to a value above 7.5 but below 9 to precipitate beryllium hydroxide and a minor portion of impurities from the leach liquor, separating the impure beryllium hydroxide, and treating the separated beryllium hydroxide to eliminate impurities.

10. A process according to claim 9, wherein the impure beryllium hydroxide is digested in a strong sodium hydroxide solution for a period sufficient to dissolve substantially all the beryllium, the resulting strong caustic beryllium solution is diluted to about 1.5 N NaOH, and the diluted solution is hydrolyzed to cause precipitation of beryllium hydroxide.

11. A process according to claim 9, wherein the impure beryllium hydroxide is fumed with suflicient sulfuric acid to convert it to beryllium sulfate, the sulfate thus obtained is dissolved in water containing a chelating agent for impurities present, and the pH of the resulting water solution is raised to about 7.0 to 8.0 thus precipitating beryllium values in the form of hydroxide.

References Cited UNITED STATES PATENTS 2,148,520 2/ 1939 Windecker 23-24 B 3,116,111 12/1963 Morana et al 23183 2,974,011 3/ 1961 Riabovol 23-24 B 3,059,998 10/1962 Mod et a1. 23-183 FOREIGN PATENTS 926,392 5/ 1963 Great Britain 23-24 B OTHER REFERENCES Crocker et al., Bureau of Mines, RI6322, 1963, pp. 1 to 9 of interest.

HERBERT T. CARTER, Primary Examiner US. Cl. X.R. 423-132 

